A cross-sectional sample of 1381 randomly chosen New Jersey adolescents born between 1961 and 1969 and equally divided by sex is followed longitudinally at three-year intervals. Originally tested between 1979 and 1981 at the ages of 12, 15, and 18, the same subjects are retested after 3 years at the ages of 15, 18, and 21; in addition, those born in 1967, 1964, and 1961 are tested a third time at the ages of 18, 21, and 24 respectively. A wide range of alcohol, marijuana and other drug use behaviors (including consummatory behaviors, motivations for use, contexts of use and consequences of use) of participants are assessed. In addition, selected variables indicating physiological functioning and health status, psychological states and traits, psychosocial-behavioral functioning and sociocultural influences are tapped using an extensive test battery. The selection of these variables is based on two criteria: (a) variables that have been implicated by previous empirical and theoretical work as determining factors in the development of alcohol and other drug using behaviors, and (b) variables measuring various aspects of human development from adolescence into adulthood that may be affected by use behaviors. Cross-sectional and limited longitudinal analyses during the first year of this project will focus on: identifying patterns and consequences of use: documenting developmental changes (including stability and continuity) in consummatory and supporting behaviors; delineating the nature of problem use; identifying intrapersonal and extrapersonal factors related to normative and problem use; examining the relationship between using status and deviant behaviors (including criminogenic behaviors); and, testing the adequacy of current theoretical models in accounting for development of normative and problem use patterns. Once a sufficiently large longitudinal data base is established, analyses will center on the identification of patterns of reciprocal interactions between the development of use behaviors on the one hand and physical, psychological, and social development of individuals on the other. Valid findings such as those to be generated from this project will provide a knowledge base significant in its own right and one relevant with regard to the design and delivery of intervention programs.